Down-the-hole drilling (DTH) essentially involves a drilling hammer at the bottom of a drill string. It relies on three elements for drilling holes: bit loading (weight), rotation and air. These active elements combine to be efficient at crushing rock. As the drill string slowly rotates, the drilling hammer is forced into the rock repeatedly. Striking power is provided by compressed air driving a piston inside the hammer.
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DTH drilling is often used in the mining industry (blast hole drilling), on construction sites, drilling water wells, and in the oil and gas industry.
DTH drilling offers several advantages over top-hammer drilling for larger, deeper holes in medium-hard formations. Because the hammer is at the bottom of the hole, power loss is minimal as the hole deepens. That means energy is not lost in the drill string and penetration rates do not markedly decline with depth—provided that back pressure does not rise significantly in the borehole. DTH drilling is most suitable for hole diameters of 4–10 inches, with some exceptions.
The DTH hammer is pneumatically powered, with the compressed air propelling it forward to impact and fracture rock. Compressed air also travels through the drill bit into the hole (air exhaust), which blows the chips and dust out of the hole.
From environmental and social perspectives, DTH is a good option because it produces much less noise and vibration than many other drilling methods. Quieter drilling means it is often the preferred drilling method when used in cities and populated areas.
FRD USA offers Tier IV and Tier III (for Central America/the Caribbean) DTH drills. Learn more here or contact us at 800.358.4476.
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DTH Boring Machine, you may not have heard much about this equipment, right? It is a kind of drilling machine, which is often used for drilling rock anchor holes, bolt holes, blast holes, grouting holes and so on in urban construction, railways, highways, rivers, hydropower and other projects. Today, we will give you a specific introduction to the DTH Boring Machine.
The drilling tool of the DTH boring machine is composed of a drill pipe, a button bit and an impactor. When drilling, use two drill rod extensions to drill into the stainless-steel plate. The rotary air supply mechanism is composed of a rotary motor, a rotary reducer, and an air supply gyrator. The slewing reducer is a three-stage cylindrical gear enclosed heterosexual component, which is automatically lubricated with a spiral oiler. The air supply gyrator is composed of a connecting body, a sealing element, a hollow main shaft and a drill pipe joint and so on, on which there is a pneumatic clamp for connecting and unloading the drill pipe.
The lifting pressure regulating mechanism is realized by the lifting motor by the lifting reducer, lifting chain, and the turning mechanism as well as the drilling tool. In the closed chain system, there is a pressure regulating cylinder, a movable pulley block, and a waterproofing agent. During normal operation, the piston rod of the pressure regulating cylinder pushes the movable pulley block to realize the decompression drilling of the drilling tool.
The working principle of the DTH boring machine is the same as that of an ordinary hydraulic rotary hammer drill. The hydraulic rotary hammer drill combines the impact rotation mechanism, and the impact energy is transmitted to the drill bit through the drill rod; while the hydraulic DTH drill separates the impact mechanism (impacter) and dives into the bottom of the hole. No matter how deep the hole is, the drill bit is directly installed on the impactor, and the impact energy is not transmitted through the drill pipe, thus reducing the impact energy loss.
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